SRD:Banded Mail of Luck
From D&D Wiki
|This material is published under the OGL 1.0a.
Banded Mail of Luck: Ten 100-gp gems adorn this +3 banded mail. Once per week, the armor allows its wearer to require that an attack roll made against him be rerolled. He must take whatever consequences come from the second roll. The wearer’s player must decide whether to have the attack roll rerolled before damage is rolled.